An absolutely necessary and important observational criterion for the correct processing of yarn in a yarn processing machine, such as a two-for-one twister having spindle assembly stations in which each include a spindle assembly for carrying a package of yarn to be withdrawn and processed while producing a rotating balloon of the yarn around the package and having a hollow carrier mechanism for supporting the package of yarn to be processed and providing a passageway for receiving the yarn as it is withdrawn from the package and a driven rotor mechanism supporting the carrier mechanism and rotating relative thereto and including a yarn reserve disc providing a passageway for the yarn therethrough from the carrier mechanism and for storing a length of yarn therearound prior to the formation of the balloon of yarn, is observation of the amount of yarn storage on the reserve disc.
This yarn storage is, as is well known, the equalizing factor between internal drawing off tension of the yarn from the supply package and the yarn balloon forces. Excess or too little yarn storage gives rise to adverse consequential phenomina which results in yarn breakage. Yarn storage must be individually adjusted taking into account yarn quality, the rotational speed of the rotor mechanism of the spindle assembly and also, in part, the drawing-off velocity which is determined by the conventional take-up mechanism in the spindle assembly.
The determination of the yarn storage, i.e. essentially the determination of the angle of wrap of the yarn around the reserve disc, is at present carried out by observation through a stroboscope, and, depending upon the angle of wrap or the amount of yarn around the reserve disc, the rotational speed of the rotor mechanism of the spindle assembly is varied, or alternatively the interior drawing-off tension of the yarn is equalized by means of a yarn break within the spindle assembly.
In certain cases, particularly spindle assemblies which are encapsulated by double walls for noise, moisture, temperature, etc. conditions, it is no longer possible to exercise a purely visual inspection of the storage of yarn around the reserve disc unless the spindle assembly is provided with access apertures in the encapsulating walls, which would partially nullify the desired effect of the encapsulation.